Manufacture of cast iron



Patented July 10, 1951 2,560,471 MANUFACTURE OF CAST IRON 3 can Georges Platon, Paris, France No Drawing. Application March 10, 1947, Serial No. 733,721. In France March 21, 1946 5 Claims. (01. '25-'41) The present invention relates to the manufacture of cast iron in blast furnaces.

It is known that the normal working of blastfurnaces entails the blowing, through nozzles opening out in the above part of the hearth, of air which has been previously heated up to more or less high temperatures according to the nature of the burden, the nature of the desired castiron and the quantity of fuel introduced into the furnace with respect to that of the metalli'ferous materials. The regulating of the working of the furnace is obtained by correctly proportioning these various factors with respect to one another. Thus, for instance, when the cast-iron is too hot, which may lead, among others, to exaggerated silicon contents, it is possible to reduce either the temperature of the wind or the quantity of coke per ton of metal to be obtained. Reversely, it is possible to increase the temperature or chemical heat of the produced castiron through increasing the temperature of the wind or the said quantity of coke. In either case, the distribution of temperatures inside the blastfurnace depends on the method of action which has been chosen.

It is also known that it is possible to act almost instantaneously on the temperature and the chemical composition of the cast-iron produced in a blast furnace by introducing liquid or vaporized water in the blasting nozzles or at the level of the latter, even in small quantities. This cooling action of water which appears in the hearth is besides accompanied by a heating action in the higher parts of the furnace, due to the indirect reduction of the ore and to the partial reconstitution of the water which has been dissociated when introduced through the nozzles.

It is further well known that the blowing of oxygen through the nozzles of a blast-furnace has been used as an assistance means in case of hangings or scaifoldings and further as a means for accelerating the working of the'furnace and modifying the distribution of temperatures in the charges. But for a predetermined burden the increase of the oxygen content of the normally blown wind cannot be very great because of the cooling of the charges above the Working zone, of the danger of hangings and of the resulting Working troubles.

One object of the present invention is to provide a method for regulating the working of a blast furnace in a particularly rapid and effective Way.

Another object is to provide a method which allows the use for permanent blowing into a blast furnace, of over oxygenated air the oxygen contents of which is higher than that which it has been possible to contemplate hitherto.

Still another object of the invention is to provide a method for the working of a blast-furnace, in which no special care has to be taken 2 regarding the lower temperature limit of the wind blown into said furnace.

The normal blast furnaces of current types are often provided with two rows of nozzles, viz. a normal row and an emergency row, the latter being generally placed above the first and being used, as shown by its nameLonIy in case of accidents in the working, such as a hanging or scaffolding of the charge.

Now, I have found according to the present invention, that great improvements in the conducting of a blast furnace may be obtained by continuously blowing air into said furnace through at least two levels of nozzles, the higher level being considered, generally speaking, as the normal blowing level and the lower level or levels as levels for controlling the conditions of manufacturing the cast-iron.

7 Experiments have shown that, in such case, the

chemical and physical states of the cast-iron in a blast furnace are very readily. influenced by any variations in the blowing conditions at the lower level or levels of nozzles.

Thus when normal air is used for blowing into the furnace, controlling of the working of the latter may be obtained very rapidly and effectively through varying the temperature of the wind at the lower level.

According to another feature of the invention liquid or vaporized water may be introduced into the furnace simultaneously with the air, substantially at the same levels. In this case, the air blown into the furnace may be at a higher temperature than that of the air which would normally be used for the considered manufacture according to the usual conditions of working, the temperature of the cast-iron being controlled {through acting upon the quantity of water introduced at each level of nozzles distinctly, and more particularly at the lower level.

The introduction of water may be carried out either through the air nozzles of the different levels, or through special nozzles or like devices provided substantially at the same levels as the air nozzles.

The quantities of water which should be introduced at each level together with the air, as well as the necessary variations of said quantities in the course of operations depend on a number of factors, among others the temperature of the wind, the composition of the burden, the quantity of fuel perton of metal to be obtained, and said quantities and variations have to be determined experimentally in each particular case, bearing in mind that any increase of the quantity of water injected in the furnace leads to a reduction of the temperature of the cast iron and vice-versa.

By way of example, the case may be considered of a blast-furnace provided with two levels of nozzles at 1.50 m. one above the other, used for producing cast-iron for which, in normal blowing conditions through a single level of nozper 1000 cubic meters of air being introduced through the lower level, in which conditions. the

temperature of the cast-iron may be controlled with precision through variations of the second order of the latter quantity of steam. It is thus possible to obtain, in the whole working of the furnace, the most economical conditions. It is also possible to correct very rapidly the accidental anomalies which may appear during the manufacture of the cast iron, as' to the physical state or the chemical composition of the cast iron. Thus, it has been possible, in less than a quarter of an hour, because of an increase of the quantity of steam introduced with the air at the lower blowing level, which increase was sufficient to produce a decrease of a few hundred degrees in the temperature of theoretical combustion at the said level, there was obtained a decrease of the order of 0.30 of the contents of silicon in the castiron, accompanied by an increase of 0.150 of the sulphur contents. A decrease of the quantity of steam would lead, in the same conditions, to an increase of the'silicon contents and a decrease of the sulphur contents.

It should be remarked that, if it is desired to use the possibilities offered by the method according to the invention for rapidly controlling the respective silicon and sulphur contents of the cast-iron, it is necessary to take into account 1 the fact that the relative quantities of slag and cast-iron which are present in the furnace are influential in such chemical reactions. Thus, in order to carry out adesulphurization by increasing the heat, the operation should take place in presence of a large quantity, of slag, before tapping of the latter. In order to reduce the silicon contents of the cast iron through cooling, the operation should be, on the contrary, carried out after tapping of the slag, in presence of a small quantity of the latter.

The method according to the invention also allows the use of over-oxygenated air for permanent blowing into the furnace, while avoiding the risk of producing systematically too hot cast-iron and of the phenomenon known as cold shaft (in French cuve froide) extending beyond the possibilities of correction through modification of the nature of the burden, said phenomenon consisting in a cooling of the charges above the working zones of the furnace due to an excessive oxygen content of the wind blown. In the case when over-oxygenatedair is used as permanent blowingmeans of'the furnace according to the invention, through two or more levels of nozzles, the reduced zone of high temperatures in the hearth is extended. The oxygen contents of theair should preferably be different from one level to another, the air blown through the lower nozzles being normally richer in oxygen than that blown through the upper nozzles.

What I claim is:

1. A process for the manufacture of cast iron in a blast furnace from a mixed charge of coke, ore and fluxes, which comprises continuously blowing air, at least as rich in oxygen as normal air, into said furnace through nozzles disposed at at least two different levels in the smelting zone of said furnace, the air blown through at least one level of nozzles being overoxygenated,

4 and controlling the temperature in the furnace by controlling the temperature of the air blown through nozzles at one level.

2. A process for the manufacture of cast iron 7 in a blast furnace from a mixed charge of coke,

ore and fluxes, which comprises continuously blowing air, at least as rich in oxygen as normal air, into said furnacethrough nozzles disposed at at least two different levels in the smelting zone of said furnace, the air blown through at least one level of nozzles being overoxygenated, and controlling the temperature in the furnace by controlling the temperature of the air being blown by introducing substantially at the same level as the air, measured quantities of water.

3. A process for the manufacture of cast iron in a blast furnace from a mixed charge of coke,

ore and fluxes, which comprises continuously blowing air, at least as rich in oxygen asnormal air, into said furnace through nozzles disposed at at least two different levels in the smelting zone of said furnace, the air blown through. at least one level of nozzles being overoxygenated, and controlling the temperature in the furnace by.

controlling the temperature of the blown air by introducing substantially at the same level as the air, measured quantities of steam.

4. A process for the manufacture-of cast iron in a blast furnace from a mixed charge of coke,

- ore and fluxes, which includes the steps of continuously blowing air at least as rich in oxygen as normal air, into said furnace through nozzles disposed at at least two different levels in the smelting zone of said furnace, the air blownthrough atleast one level of nozzles being overoxygenated, and the oxygen contentof the air blown through the nozzles disposed at different levels being different, one from the other.

5. A process for the manufacture of cast iron in a blast furnace from a mixed charge of coke, ore and fluxes, which includes the steps of continuously blowing air at least as rich in oxygen as normal air, into said furnace through nozzles disposed at at least two different levels in the smelting zone of said furnace, the air blown through at least one level of nozzles being overoxygenated, and the oxygen content and the temperature of the air blown through the nozzles disposed at different levels being different, one from the other.

JEAN GEORGES PLATON.

REFERENCES CITED The following references are of recordin the file of this patent:

UNITED STATES PATENTS Number Name Date 1,092,168 Prudhomme Apr. 7, 1914 1,230,431 Pictet June 19, 1917 1,507,740 Kirby Sept. 9, 1924 1,518,854 Kirby Dec. 9, 1924 1,695,953 Feild Dec. 18, 1928 1,917,642 Furnas July 11, 1933 1,921,212 Brassert Aug. 8; 1933 FOREIGN PATENTS Number Country Date 7556/ 27 Australia 444,809 France Aug. 17, 1912 457,645 France July 18, 1913 868,862 France Oct. 20, 1941 3,660 Great Britain 01 1879 306,892 Great Britain 1930 (Not accepted) 

1. A PROCESS FOR THE MANUFACTURE OF CAST IRON IN A BLAST FURNACE FROM A MIXED CHARGE OF COKE, ORE AND FLUXES, WHICH COMPRISES CONTINUOUSLY BLOWING AIR, AT LEAST AS RICH IN OXYGEN AS NORMAL AIR, INTO SAID FURNACE THROUGH NOZZLES DISPOSED AT AT LEAST TWO DIFFERENT LEVELS IN THE SMELTING ZONE OF SAID FURNACE, THE AIR BLOWN THROUGH AT LEAST ONE LEVEL OF NOZZLES BEING OVEROXYGENATED, AND CONTROLLING THE TEMPERATURE IN THE FURNACE BY CONTROLLING THE TEMPERATURE OF THE AIR BLOWN THROUGH NOZZLES AT ONE LEVEL. 